A soft contact lens (hereinafter referred to as lens) has some apprehensions that eyes are injured when the lens is continuously worn in eyes as it is for a long period of time because stains in the surroundings, microbes, proteins contained in tear fluid, and the like adhere to the lens while the lens is worn in eyes. Accordingly, there is a necessity to clean or disinfect the lens regularly, preferably every day.
As a method for cleaning a lens, a method comprising washing a lens with a solution containing a surface active agent by fingers has been conventionally carried out, and according to the method, stains on the surface of the lens can be removed. However, stains such as proteins got into the internal of a lens cannot be removed. Further, when the lens is boiled to disinfect as it is, denaturation or coagulation of the proteins being got into a lens proceeds, and denatured proteins or coagulated proteins are more stiffly adhered to the lens. As a result, there occurs a problem of generation of cloudiness of the lens.
As a cleaning agent for reusing a lens stained with proteins, a cleaning agent containing a proteolytic enzyme has been conventionally known. However, according to the cleaning method of using this cleaning agent, although proteins adhered to the surface of a lens can be decomposed, besides taking a long period of time for revealing the cleaning effects, sufficient removing effects of proteins cannot be revealed because the proteolytic enzyme itself should be immersed into the internal of a lens so that proteins being denatured in the internal of a lens can be decomposed.
Also, U.S. Pat. No. 4,732,185 discloses a method for cleaning a lens comprising establishing an electric field in a determined direction in a boric acid-EDTA buffer solution having a range of pH 8 to 9 and immersing a lens in the solution to remove proteins from the lens by electrophoresis. When this method is carried out, contaminated proteins in the internal of the lens can be removed. However, the method requires that proteins should not be denatured nor ionized, and there are some problems in the method such that it takes a long period of time for the treatment. Further, according to the method disclosed in the above U.S. Patent, boric acid is used in a high concentration such as 0.808 mol/l and pH is kept at an alkaline level of 8 to 9 so that a lens can be disinfected by antiseptic effect and disinfecting effect of boric acid because the lens cannot be heated to prevent thermal denaturation of proteins. When boric acid is used in such a high concentration, disinfecting effect is exhibited. However, since pH and/or osmotic pressure are/is too high, wearing a lens in eyes after the treatment is dangerous, and there is a problem in safety for eyes.
On the other hand, as a method for disinfecting a lens, a method comprising immersing a lens in a sodium chloride aqueous solution and generating hypochlorite by applying an electric current to the solution to disinfect the lens, disclosed in Japanese Unexamined Patent Publication No. 68454/1981 and Japanese Unexamined Patent Publication No. 153658/1982, a method comprising immersing a lens in an H.sub.2 O.sub.2 aqueous solution to disinfect the lens and decomposing H.sub.2 O.sub.2 with a metallic catalyst, a reducing agent and an enzyme catalyst to make the solution harmless, disclosed in Japanese Unexamined Patent Publication No. 38559/1983, Japanese Unexamined Patent Publication No. 68858/1985 and Japanese Unexamined Patent Publication No. 217333/1985, and the like have been known other than the above-mentioned method for disinfecting a lens comprising boiling a lens to disinfect.
However, according to the method of generating hypochlorite by electrolysis, it takes a long period of time for the natural disappearance of hypochlorite remaining in a treating vessel after disinfecting, and the procedures are also complex because the solution should be reduced so that hypochlorite does not remain in a lens. Further, when the above procedures are applied to a colored contact lens or a dye-marked lens, there are some problems such that decoloration or discoloration of the colored lens or the dye-marked lens occurs due to the above treatment.
Also, according to the method of using an H.sub.2 O.sub.2 aqueous solution, besides taking a long period of time for the treatment since H.sub.2 O.sub.2 remaining in the lens should be decomposed, stimulation such as smarting of eyes occurs if H.sub.2 O.sub.2 remaining in the internal of the lens is not completely decomposed. Therefore, the above method is not a suitable disinfecting method.
As a soaking solution for soft contact lenses, saline solution; liquid agents prepared by adding a preservative such as thimerosal, chlorhexidine, methylparaben, propylparaben or sorbic acid, and a chelating agent such as ethylene diaminetetraacetic acid, gluconic acid or citric acid to saline solution; liquid agents prepared by dissolving a tablet of the above-mentioned compounds in purified water or distilled water on use, and the like have been known.
However, when a soft contact lens is immersed in these soaking solutions for soft contact lenses and a direct current is applied to the solutions to clean and disinfect the soft contact lenses, chlorine ion existing in the solutions forms hypochlorite, and thereby there occurs some problems that the hypochlorite deteriorates the material of the soft contact lenses, and further colored soft contact lenses or dye-marked soft contact lenses are decolored or discolored.
It is an object of the present invention to provide a method of cleaning a lens giving no wrong influence to eyes, having safety for eyes and excellent detergency, and also disinfecting the lens.
Also, it is the second object of the present invention to provide a treating solution for soft contact lenses giving no wrong influence to eyes, having safety for eyes, and also giving no wrong influences to soft contact lenses when the soft contact lenses are electrically treated.
Further, it is the third object of the present invention to provide a treating solution for soft contact lenses having a property mechanically distinguishable from conventional treating solutions for soft contact lenses when the conventional treated solutions are misguidedly used.